초록
<P><B>Abstract</B></P> <P>This paper describes a new option for integrated recovery and esterification of carboxylates produced by anaerobic digestion at a pH above the pK<SUB>a</SUB>. The carboxylates (acetate, propionate, butyrate, valerate and lactate) are recovered using a strong anion exchange resin in the bicarbonate form, and the resin is regenerated using a CO<SUB>2</SUB>-expanded alcohol technique, which allows for low chemicals consumption and direct esterification. Paper mill wastewater was used to study the effect of pH and the presence of other inorganic anions and cations on the adsorption and desorption with CO<SUB>2</SUB>-expanded methanol. Calcium, which is present in paper mill wastewater, can cause precipitation problems, especially at high pH. Esters yields ranged from 1.08±0.04mol methyl acetate/mol of acetate<SUB>in</SUB> to 0.57±0.02mol methyl valerate/mol of valerate<SUB>in</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Paper mill wastewater was treated with an anaerobic mixed culture fermentation. </LI> <LI> Carboxylic acids were produced at a pH above their pK<SUB>a</SUB>. </LI> <LI> Carboxylates salts were recovered using a strong anion exchange resin. </LI> <LI> The resin is regenerated and esters were produced using CO<SUB>2</SUB>-expanded methanol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>